The 15th Global Conference on Materials Science and Engineering (CMSE 2026)

Abstract: Metallic glasses (MGs) could be obtained by quenching from the melt at a rate high enough to suppress nucleation/growth of crystalline phases, and they have a glass-like amorphous structure. Because of the amorphous structure, MGs have no grain boundaries/dislocations and hence possess very high strength (~2 GPa). Also, like glasses, MGs have polymer-like viscous flow behavior at temperatures above the glass transition temperature, T_g. MGs provide a challenge of engineering applications for their unique structure and properties. However, plasmonic applications have been rarely explored for MGs. In this work, we unveiled that certain compositions of Au-based MGs possessed negative dielectric constants and could be used as plasmonic materials. Furthermore, with a low glass transition temperature of Au-based thin film MGs (TFMGs), we were able to fabricate large dimensions of nanostructures using an inexpensive thermal imprint method in air instead of other costly lithography methods.

We fabricated fully amorphous AuCuSi TFMGs using magnetron sputtering, and performed nanoindentation creep tests in the temperature range of 50 ºC to 170 ºC to characterize the viscous flow behavior and to determine the T_g of the film. We fabricated nanostructures by thermal imprinting on the film at a temperature slightly above the T_g, and conducted both measurements and simulations to demonstrate that our fabricated nanostructures were suitable for surface-enhanced Raman scattering (SERS) applications. It is worth noting that in the absence of grain boundaries in amorphous TFMGs, damping due to increased scattering at grain boundaries does not occur and SERS could be improved. Also, compared to regular SERS substrates of textured Si with deposited Au films, imprinted Au-based TFMGs provided complete coverage of Si underneath and the vibrational signal of Si lattice would not show in Raman spectra to possibly overlap signals of analyte and decrease the accuracy of sensing. Our results suggested new avenues for applying a low-cost and high-throughput method on AuCuSi TFMGs to fabricate large dimensions of substrates for plasmonic applications.

Keywords: Thin film metallic glasses, sputtering, Nanoindentation, thermal imprint, surface-enhanced Raman scattering.

Acknowledgements: This work was supported by the National Science and Technology Council, Taiwan under Contract no. NSTC 115-2221-E-002-032

Biography: Professor Chun-Hway Hsueh received his PhD degree from the University of California, Berkeley in 1981. He is currently an Emeritus Professor in Department of Materials Science and Engineering, National Taiwan University (NTU). Before joining NTU in 2010 as a Distinguished Professor, he was a Distinguished R&D Staff at Oak Ridge National Laboratory. Professor Hsueh’s area of expertise is to develop analytical models and to derive closed-form solutions to describe the thermomechanical properties and performance of materials as functions of the essential parameters. Since joining NTU, his research has been extended from theoretical to applied research. His current research work includes metallic glasses, high entropy alloys, nanoindentation, surface-enhanced Raman scattering, and plasmonics nanodevices. Professor Hsueh is Academician of the World Academy of Ceramics (WAC), Academician of the Asia Pacific Academy of Materials (APAM), Fellow of the American Society for Metals (ASM) International, Fellow of the American Ceramic Society (ACerS), Fellow of the World Innovation Foundation (WIF), and Fellow of the Materials Research Society, Taiwan (MRS-T).